The present invention relates to a scroll type fluid machine, and, more particularly, to a scroll compressor of a hermetic type for use in a fluid machine such as an air conditioning machine, a refrigerating apparatus and the like, which includes a hermetically closed low pressure vessel suitable for managing or controlling a thrust force generated in scroll members of the compressor.
In a scroll compressor which comprises an orbiting scroll member and a stationary scroll member each having a spriral wrap, when a gas in the compressor is compressed, the compressed gas generates a force or thrust force which acts to move both a scroll members apart from each other.
In, for example, U.S. Pat. No. 4,365,941, an arrangement is proposed for overcoming the thrust force and permitting the compressor to continue the compressing operation, wherein a back pressure chamber is provided in the back of the orbiting scroll member. The back pressure chamber is hermetically sealed against other portions of the compressor so as to maintain the space of the back pressure chamber at an intermediate pressure higher than the suction pressure of the compressor but lower than the discharge pressure thereof.
In order to apply such a method to a method to a scroll-type fluid machine in which the space in the hermetically closed vessel is maintained at a low pressure, however, it is necessary to improve the compressor so that it has a mechanically suitable construction therefor.